@trainjunkie there is this Mod already; http://www.train-fever.net/filebase/index.php/Entry/10-Cost-mod/
But not sure if you aiming for some thing as he is or whatnot. I know in that its Running cost for ALL and not Train focus. But then there is also this; http://www.train-fever.net/filebase/index.php/Entry/29-Halbierte-Betriebskosten-f%C3%BCr-Lokomotiven-Trams-Waggons-und-Busse-Lowered-running/
So you’d have to see. Personally I tried both, and i don’t know. Just didn’t feel right, even when editing them myself to adjust numbers. Rather learn Vanilla more. Plus I am learning to make money in those bad parts/not spamming trains. Which I’d love too do, but to get a mod to do so, which also is 100% profit… kinda ruins the fun.